Anterior cruciate ligament tears (ACL)
The anterior cruciate ligament (ACL) sits inside the knee and stabilises it during sudden changes of direction or quick stops.
An ACL tear is often painful and causes a swollen and stiff knee for the first few days.
ACL tears need to be assessed by a physiotherapist or orthopaedic surgeon as soon as possible. Even if it doesn’t need surgery, the best recovery comes from starting rehab early.
The anterior cruciate ligament (ACL) sits inside the knee and helps stabilise it, especially during sports that involve sudden changes of direction or quick stops.
The knee joint is made up of three bones – the thighbone (femur), shinbone (tibia) and kneecap (patella) – and is stabilised by four main ligaments.
The anterior and posterior cruciate ligaments (ACL and PCL) sit in the middle of the knee and control its back and forth motion, stopping it from giving way. The medial and lateral collateral ligaments (MCL and ACL) are on the outside of the knee, resisting sideways motion and bracing it against unusual motion.
A ligament injury can be:
- Grade 1 – a sprain
- Grade 2 – a partial tear
- Grade 3 – a complete rupture
ACL injuries are usually intact or torn, rarely a partial grade 2 injury. Your specialist will grade the injury clinically – this grading may be different to the grades used by radiologists in their MRI scan reports.
ACL tears are one of the most common knee injuries in sport. They usually occur in non-contact situations when the knee twists and bends at the same time. This can happen when:
- Changing direction rapidly (cutting/pivoting)
- Stopping suddenly
- Landing from a jump (common in netball)
- Colliding directly (such as a rugby tackle)
Athletes in high-demand sports like soccer, rugby, basketball, and netball are more likely to injure their ACL. Studies have shown that female athletes are at higher risk for anatomical and physiological reasons.
You may have felt your knee give way or buckle beneath you and heard a ‘pop’ as the ligament snapped – this can be painful but is not always. You may not be able to take weight through your knee and need support from others or crutches to walk. If you managed to play on, your knee may have felt unstable or given way.
The knee will swell in the first 24 hours and can remain swollen for weeks, depending on the injury’s severity and whether other ligaments or cartilage are damaged. The swelling makes the knee stiff and difficult to fully straighten or bend.
Your specialist will ask how the injury occurred: a twisting injury and a ‘pop’ usually mean a torn ACL or a dislocated kneecap. They will also ask about your general health and previous knee and joint injuries. It’s important to detail your recreational and sporting activities and their competitive level – this can change your treatment options and recovery timelines.
The specialist will perform a physical examination of the knee. This will usually demonstrate the ACL injury and any associated damage.
A specialist will always want an MRI scan to check for associated cartilage, meniscus, and other ligament injuries. It is common to have an x-ray as well – this is the easiest imaging to get quickly and can rule out a fracture.
The first stage of treatment is to settle the knee down which involves treating the swelling and the stiffness. It is vital to engage a physiotherapist as early as possible. We help you to settle your knee down so that it can be used for day to day activities without pain. This involves anti-inflammatories such as ibuprofen, diclofenac or meloxicam for 1 to 2 weeks, which reduces swelling and pain – please check with your doctor or specialist that these medicines are safe for you first. Some compression bandaging can be useful, as can ice packs.
The strength of the quadriceps muscle which protects the knee will disappear quickly without appropriate training and the swelling will make the knee stiff unless it is managed. Specific exercises as part of a comprehensive prehab and rehab program will aim to strengthen the surrounding leg muscles and restore function to the knee joint.
A torn ACL will not heal. In some cases, it can stick to surrounding tissue such as the PCL and confer some level of stability to the knee. This can be enough for some, especially the older and lower demand patients.
It is possible to be active with a stable knee without a functioning ACL. This can include running, swimming, cycling and even skiing. It is all about how stable each patient’s knee is when being used.
However, younger patients who want to continue to compete in sports which involve sudden changes in direction or speed of travel, often struggle without having reconstruction surgery. They will be offered an ACL reconstruction.
We have specialty knee rehab programs here at MTP Health to treat patients with ACL injuries that are planning to have surgery and those that are going to trial activity without surgery.
A torn ACL will not heal. In some cases, it can stick to surrounding tissue such as the PCL and confer some level of stability to the knee. This can be enough for some, especially the older and lower demand patients.